Recording and retrieval of sound data in a hearing prosthesis

ABSTRACT

A hearing prosthesis for delivering stimuli to a hearing-impaired recipient is disclosed, the hearing prosthesis comprising: a sound transducer for converting received sound signals into electric audio signals; a sound processor for converting said electric audio signals into stimuli signals; a stimulator for delivering said stimuli to the recipient; a memory for storing data representative of sound signals; and a controller configured to cause selected sound data to be retrieved from said memory and processed by said sound processor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/461,182, entitled “Recording and Retrieval of Sound Data ina Hearing Prosthesis”, filed on May 1, 2012, which is a divisional ofU.S. patent application Ser. No. 11/402,836 entitled “Recording andRetrieval of Sound Data in a Hearing Prosthesis”, filed on Apr. 13,2006, now U.S. Pat. No. 8,170,677, which claims the priority ofAustralian Patent No. 2005901833 entitled, “Enhanced Hearing ProsthesisSystem,” filed Apr. 13, 2005, and Australian Patent No. 2006900982entitled, “Hearing Prosthesis with Improved System Interface” filed Feb.28, 2006,” which are hereby incorporated by reference herein in theirentireties.

The present application makes reference to is related to InternationalPublication Nos. WO0097/001314 and WO2002/054991, and U.S. Pat. Nos.4,532,930, 6,537,200, 6,565,503, 6,575,894 and 6,697,674, which arehereby incorporated by reference herein in their entireties.

BACKGROUND

1. Field of the Invention

The present invention relates generally to hearing prostheses, and moreparticularly, to recording and retrieval of sound data in a hearingprosthesis.

2. Related Art

Hearing loss, which may be due to many different causes, is generally oftwo types, conductive and sensorineural. In some cases, a person mayhave hearing loss of both types. Conductive hearing loss occurs when thenormal mechanical pathways to provide sound to hair cells in the cochleaare impeded, for example, by damage to the ossicles. Conductive hearingloss is often addressed with conventional auditory prostheses commonlyreferred to as hearing aids, which amplify sound so that acousticinformation can reach the cochlea.

In many people who are profoundly deaf, however, the reason for theirdeafness is sensorineural hearing loss. This type of hearing loss is dueto the absence or destruction of the hair cells in the cochlea whichtransduce acoustic signals into nerve impulses. Those suffering fromsensorineural hearing loss are thus unable to derive suitable benefitfrom conventional hearing aids due to the damage to or absence of themechanism that naturally generates nerve impulses from sound. As aresult, hearing prostheses have been developed to provide persons withsensorineural hearing loss with the ability to perceive sound.

Hearing prostheses include but are not limited to hearing aids, auditorybrain stimulators, and Cochlear™ prostheses (commonly referred to asCochlear™ prosthetic devices, Cochlear™ implants, Cochlear™ devices, andthe like; simply cochlea implants herein.) Cochlear implants use directelectrical stimulation of auditory nerve cells to bypass absent ordefective hair cells that normally transduce acoustic vibrations intoneural activity. Such devices generally use an electrode array insertedinto the scala tympani of the cochlea so that the electrodes maydifferentially activate auditory neurons that normally encodedifferential pitches of sound. Auditory brain stimulators are used totreat a smaller number of recipients with bilateral degeneration of theauditory nerve. For such recipients, the auditory brain stimulatorprovides stimulation of the cochlear nucleus in the brainstem.

Cochlear implants typically comprise external and implanted or internalcomponents that cooperate with each other to provide sound sensations toa recipient. The external component traditionally includes a microphonethat detects sounds, such as speech and environmental sounds, a speechprocessor that selects and converts certain detected sounds,particularly speech, into a coded signal, a power source such as abattery and an external transmitter antenna.

The coded signal output by the speech processor is transmittedtranscutaneously to an implanted receiver/stimulator unit, commonlylocated within a recess of the temporal bone of the recipient. Thistranscutaneous transmission occurs via the external transmitter antennawhich is positioned to communicate with an implanted receiver antennadisposed within the receiver/stimulator unit. This communicationtransmits the coded sound signal while also providing power to theimplanted receiver/stimulator unit. Conventionally, this link has beenin the form of a radio frequency (RF) link, although other communicationand power links have been proposed and implemented with varying degreesof success.

The implanted receiver/stimulator unit also includes a stimulator thatprocesses the coded signal and outputs an electrical stimulation signalto an intra-cochlea electrode assembly. The electrode assembly typicallyhas a plurality of electrodes that apply electrical stimulation to theauditory nerve to produce a hearing sensation corresponding to theoriginal detected sound. Because the cochlea is tonotopically mapped,that is, partitioned into regions each responsive to stimulation signalsin a particular frequency range, each electrode of the implantableelectrode array delivers a stimulating signal to a particular region ofthe cochlea.

In the conversion of sound to electrical stimulation, frequencies areallocated to stimulation channels that provide stimulation current toelectrodes that lie in positions in the cochlea at or immediatelyadjacent to the region of the cochlear that would naturally bestimulated in normal hearing. This enables the prosthetic hearingimplant to bypass the hair cells in the cochlea to directly deliverelectrical stimulation to auditory nerve fibers, thereby allowing thebrain to perceive hearing sensations resembling natural hearingsensations.

While developments in signal processing continue to improve thecapability of conventional cochlear implant systems to augment orprovide an approximate sense of hearing for profoundly deaf persons, ithas been found that conventional systems are inherently limited in theirability to fully restore normal hearing. It is desired to improve uponexisting arrangements to enable recipients to better perceive and/orunderstand sounds of interest.

SUMMARY

In one aspect of the present invention, a hearing prosthesis fordelivering stimuli to a hearing-impaired recipient is disclosed, thehearing prosthesis comprising: a sound transducer for convertingreceived sound signals into electric audio signals; a sound processorfor converting said electric audio signals into stimuli signals; astimulator for delivering said stimuli to the recipient; a memory forstoring data representative of sound signals; and a controllerconfigured to cause selected sound data to be retrieved from said memoryand processed by said sound processor.

In another aspect of the present invention, a sound processor for ahearing prosthesis having a sound transducer for converting receivedsound signals into electric audio signals and a stimulator fordelivering stimuli to a recipient is disclosed, the sound processorcomprising: a digital signal processor for converting said electricaudio signals into stimuli signals; and a storage and retrieval systemcomprising a memory for storing sound data representative of soundsignals, a data storage module for recording selected sound data, and adata retrieval module configure to retrieve selected data from saidmemory to be processed by said sound processor.

In a further aspect of the present invention, a method for deliveringstimuli to a hearing-impaired recipient, comprising: converting receivedsound signals into electric audio signals; converting said electricaudio signals into stimuli signals; delivering said stimuli signals tothe recipient; storing data representative of said received soundsignals; retrieving selected sound data from said memory; and processingsaid retrieved sound data by said sound processor.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described herein in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a schematic block diagram of an exemplary hearing prosthesis,a cochlear implant, in which embodiments of the present invention may beadvantageously implemented;

FIG. 2A is a functional block diagram of a sound processor implementedin the sound processing unit illustrated in FIG. 1 in accordance withone embodiment of the present invention;

FIG. 2B is a functional block diagram of the sound data storage andretrieval system illustrated in FIG. 2A in accordance with oneembodiment of the present invention;

FIG. 3A is a flow chart of the operations performed by the soundprocessor illustrated in FIG. 2A in accordance with one embodiment ofthe present invention;

FIG. 3B is a flow chart of the operations performed by the sound datastorage and retrieval system illustrated in FIG. 2B in accordance withone embodiment of the present invention;

FIG. 3C is a flow chart of the operations performed by the internalcomponent assembly illustrated in FIG. 1 in accordance with oneembodiment of the present invention.

FIG. 4 is a block diagram illustrating a typical prior art cochlearimplant;

FIG. 5 is a block diagram illustrating a one embodiment of anotheraspect of the present invention for a cochlear implant;

FIG. 6 is a block diagram illustrating another embodiment of this aspectof the present invention for a cochlear implant;

FIG. 7 is a block diagram illustrating another embodiment of this aspectof the present invention for a cochlear implant;

FIG. 8 is a block diagram illustrating another embodiment of this aspectof the present invention for a cochlear implant;

FIG. 9 is a block diagram illustrating another embodiment of this aspectof the present invention for a cochlear implant;

FIG. 10 is an exemplary waveform for a segment of speech;

FIG. 11 is a signal flow diagram of the analysis part of a typicalLinear Predictive Coder (LPC);

FIG. 12 is a calculated LPC coefficients for the segment of speech shownin FIG. 4;

FIG. 13 is the 5 bit quantised LPC coefficients for the segment ofspeech shown in FIG. 4;

FIG. 14 is the calculated excitation signal for the segment of speechshown in FIG. 4;

FIG. 15 is the 6 quantised excitation signal for the segment of speechshown in FIG. 4;

FIG. 16 is a signal flow diagram of the synthesis part of the exampleLPC; and

FIG. 17 is the reconstructed LPC for the segment of speech shown in FIG.4.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of an exemplary hearing prosthesis in whichthe present invention may be implemented. The relevant components ofouter ear 101, middle ear 105 and inner ear 107 are described nextbelow, followed by a description of an implanted cochlear implant 100.An acoustic pressure or sound wave 103 is collected by outer ear 101(that is, the auricle) and channelled into and through ear canal 102.Disposed across the distal end of ear canal 102 is a tympanic membrane104 which vibrates in response to acoustic wave 103.

This vibration is coupled to oval window or fenestra ovalis 115 throughthree bones of middle ear 105, collectively referred to as the ossicles117 and comprising the malleus 113, the incus 109 and the stapes 111.Bones 113, 109 and 111 of middle ear 105 serve to filter and amplifyacoustic wave 103, causing oval window 115 to articulate, or vibrate.Such vibration sets up waves of fluid motion within cochlea 132. Suchfluid motion, in turn, activates tiny hair cells (not shown) that linethe inside of cochlea 132. Activation of the hair cells causesappropriate nerve impulses to be transferred through the spiral ganglioncells (not shown) and auditory nerve 138 to the brain (not shown), wherethey are perceived as sound.

Cochlear prosthesis 100 comprises external component assembly 142 whichis directly or indirectly attached to the body of the recipient, and aninternal component assembly 144 which is temporarily or permanentlyimplanted in the recipient.

External assembly 142 typically comprises a sound transducer 120 fordetecting sound, and for generating an electrical audio signal,typically an analog audio signal. In this illustrative embodiment, soundtransducer 120 is a microphone. In alternative embodiments, soundtransducer 120 may comprise, for example, more than one microphone, oneor more a telecoil induction pickup coils or other device now or laterdeveloped that may detect sound and generate electrical signalsrepresentative of such sound.

External assembly 142 also comprises a speech processing unit 116, apower source (not shown), and an external transmitter unit 106. Externaltransmitter unit 106 comprises an external coil 108 and, preferably, amagnet (not shown) secured directly or indirectly to the external coil108.

Speech processing unit 116 processes the output of microphone 120 thatis positioned, in the depicted embodiment, by outer ear 101 of therecipient. Speech processing unit 116 generates coded signals, referredto herein as a stimulation data signals, which are provided to externaltransmitter unit 106 via a cable (not shown). Speech processing unit 116is, in this illustration, constructed and arranged so that it can fitbehind outer ear 101. Alternative versions may be worn on the body or itmay be possible to provide a fully implantable system which incorporatesthe speech processor and/or microphone into the internal componentassembly 144.

Internal components 144 comprise an internal receiver unit 112, astimulator unit 126 and an electrode assembly 118. Internal receiverunit 112 comprises an internal transcutaneous transfer coil (not shown),and preferably, a magnet (also not shown) fixed relative to the internalcoil. Internal receiver unit 112 and stimulator unit 126 arehermetically sealed within a biocompatible housing. The internal coilreceives power and data from external coil 108, as noted above. A cableor lead of electrode assembly 118 extends from stimulator unit 126 tocochlea 132 and terminates in an array 134 of electrodes 136. Signalsgenerated by stimulator unit 126 are applied by electrodes 136 tocochlear 132, thereby stimulating the auditory nerve 138.

In one embodiment, external coil 108 transmits electrical signals to theinternal coil via a radio frequency (RF) link. The internal coil istypically a wire antenna coil comprised of at least one and preferablymultiple turns of electrically insulated single-strand or multi-strandplatinum or gold wire. The electrical insulation of the internal coil isprovided by a flexible silicone molding (not shown). In use, internalreceiver unit 112 may be positioned in a recess of the temporal boneadjacent to outer ear 101 of the recipient.

Further details of the above and other exemplary prosthetic hearingimplant systems in which embodiments of the present invention may beimplemented include, but are not limited to, those systems described inU.S. Pat. Nos. 4,532,930, 6,537,200, 6,565,503, 6,575,894 and 6,697,674,which are hereby incorporated by reference herein in their entireties.For example, while cochlear implant 100 is described as having externalcomponents, in alternative embodiments, cochlear implant 100 may be atotally implantable prosthesis. In one exemplary implementation, forexample, sound processing unit 116, including microphone 120, a soundprocessor and/or a power supply may be implemented as one or moreimplantable components.

As shown in FIG. 1, cochlear implant 100 is further configured tointeroperating with a wireless user interface 146 and an externalprocessor 142 such as a personal computer, workstation or the like,implementing, for example, a hearing implant fitting system. This isdescribed in greater detail below.

FIG. 2A is a functional block diagram of one embodiment of a soundprocessor 200 implemented in speech processing unit 116.

Sound processor 200 receives an electrical audio signal, typically ananalog audio signal, from sound transducer 120 such as microphone.

Sound processor 200 comprises a signal conditioning and digitalconversion module 202. The analog electrical audio signal is processedby conditioner and analog-to-digital (A/D) converter 202. Initially,conditioner and A/D converter 202 conditions analog electrical audiosignal and converts it into a digital audio signal.

Sound processor 116 further comprises a digital signal processor (DSP)204 configured to perform complex digital signal processing operationson digital audio signal. DSP 204 generates a processed digital audiosignal. It will be appreciated by those of ordinary skill in the artthat DSP 204 may implement digital signal processing techniques now orlater developed to generate processed audio signal.

Following the above-noted digital signal processing operations, a sounddata-to stimulus data converter 206 converts processed audio signal intoa stimulation signal suitable for delivery to stimuli transducers, suchas electrodes 136 (FIG. 1). Typically, during this conversion stage,recipient-specific parameters are applied to the signal to customize theelectrical stimulation signals for the particular recipient'srequirements.

Today, most cochlear implants require values for at least tworecipient-specific parameters to be set for each stimulating electrode136. These values are referred to as the Threshold level (commonlyreferred to as the “THR” or “T-level;” “threshold level” herein) and theMaximum Comfortable Loudness level (commonly referred to as the MostComfortable Loudness level, “MCL,” “M-level,” or “C;” simply “comfortlevel” herein). Threshold levels are comparable to acoustic thresholdlevels while comfort levels indicate the level at which a sound is loudbut comfortable. It should be appreciated that although the terminologyand abbreviations may not be used in connection with all cochlearimplants, the general purpose of threshold and comfort levels is commonamong cochlear implants: to determine a recipient's electrical dynamicrange.

These and other customizing parameters are normally determined inconsultation with a clinician, audiologist or other practitioner 144(“clinician” herein) during a clinical “mapping” procedure using ahearing implant fitting system 142. Sound data-to-stimulus dataconverter 206 may implement stimulation signal conversion and parametercustomization operations as presently employed in commercial hearingprostheses as well as such techniques as developed in the future. As oneof ordinary skill in the art would appreciate, such operations performedby conventional hearing prosthesis systems are well-known and,therefore, are not described further herein.

Stimulus signal 226 generated by sound data-to-stimulus data converter206 is applied to a stimulus data encoder 208 and link signal generator210. Stimulus data encoder 208 encodes the stimulation signal, and theencoded signals are provided to link signal transmitter 210 fortransmission to implanted stimulator unit 126. In the embodimentdescribed above with reference to FIG. 1, such transmission occurs overa transcutaneous link. In such embodiments, link signal transmitter 210comprises external coil 108 (FIG. 1) and related components.

The above-noted sound processing operations and stages 202, 204, 206 and208 are subject to control from a system controller 212. As one ofordinary skill in the art will appreciate, sound processor 200 may beused in combination with any speech strategy now or later developed,including but not limited to, Continuous Interleaved Sampling (CIS),Spectral PEAK Extraction (SPEAK), and Advanced Combination Encoders(ACE™). An example of such speech strategies is described in U.S. Pat.No. 5,271,397, the entire contents and disclosures of which is herebyincorporated by reference herein. The present invention may also be usedwith other speech coding strategies now or later developed. In oneembodiment, the present invention may be used on Cochlear Limited'sNucleus™ implant system that uses a range of coding strategiesalternatives, including SPEAK, ACE™, and CIS. Among other things, thesestrategies offer a trade-off between temporal and spectral resolution ofthe coded audio signal by changing the number of frequency channelschosen in the signal path.

System controller 212, in concert with other components of cochlearimplant 100, ensures that the time delay between sound signals 103 beingreceived by sound transducer 120 and the delivery of correspondingstimuli at implanted electrodes 136 is maintained within acceptablelimits. Too much time delay can cause discomfort and disorientation forthe recipient. In particular, when this delay is excessive the recipientcan experience further difficulties in interpreting or understandingspeech and other sounds of interest, particularly in the presence ofextraneous noise or echoes.

Hence, the minimization of such time delay improves the real-timeperformance of cochlear prosthesis 100. This may significantly limit theextent to which incoming sound 103 can be processed, particularly giventhe limited battery power available in small, light weight prostheses.

System controller 212 also comprises a sound storage and retrievalsystem 228 constructed and arranged to store sound data that isincorporated into the above-described sound processing pipeline toprovide the recipient with information that supplements, compliments orfacilitates the interpretation and understanding of sound 103. FIG. 2Bis a functional block diagram of one embodiment of sound data storageand retrieval system 228 illustrated in FIG. 2A. Embodiments of system228 will now be described with reference to FIGS. 2A and 2B.

Sound storage and retrieval system 228 configured to store or recordsound data 230A-230D selected from a sound processing stage 202, 204,206, 208, respectively. Recorded sound data 230 may be stored withassociated data (described below) in accordance with configurablestorage settings. System 228 also retrieves selected sound data232A-232D for delivery to an appropriate sound processing stage 202,204, 206, 208, respectively. Retrieved sound data 232 may be processedas necessary by sound processor 200 to generate desired stimuli to therecipient reflecting the retrieved sound signals 232.

In the embodiment illustrated in FIGS. 2A and 2B, sound data storage andretrieval system 228 exchanges data and commands with system controller212 of sound processor 200, as shown by data/command line 234. Sounddata storage and retrieval system 228 also exchanges data and commandswith programming system 142 (FIG. 1) via a programming interface 214, asshown by data/command line 236, and user interface(s) 216 controllableby the recipient.

As will be appreciated by those of ordinary skill in the art, userinterface 216 can take many different forms. For example, user interface216 can include a keypad allowing the recipient to enter necessarycommands. Alternatively, user interface 216 may allow different forms ofinteraction with the recipient to invoke commands, such as voice commandrecognition, head tilt or other user gesture recognition, etc. Userinterface 216 may be physically connected to the system. Alternativelyor additionally, user interface 216 can be in the form of a wired orwireless remote control unit 146 (FIG. 1).

As shown in FIG. 213, sound data storage and retrieval system 228comprises one or more memory modules 258 for storing sound data inaccordance with the teachings of the present invention.

As one of ordinary skill in the art would appreciate, memory module(s)258 may comprise any device, component, etc., suitable for storing sounddata 230 as described herein. For example, memory module(s) 214 maycomprise computer-readable media such as volatile or non-volatilememory. Also, memory module(s) 258 may comprise removable memorymodule(s) 258A, permanent or non-removable memory modules 258B, as wellas remove memory module(s) 258C not collocated with system 228 or,perhaps, sound processor 200.

As will be described in greater detail below, one advantage for usingremovable memory module(s) 258A such as a flash memory module is thatthe recipient or the recipient's clinician or audiologist can beprovided access to the sound data stored therein for processing oranalysis.

Sound data storage and retrieval system 228 determines which memorymodule(s) 258 to store sound data based on a memory module selectioncommand 264. Memory module selection command 264 may be generated by anyof the components or devices which system shares an interface such assystem controller 212, sound processor user interfaces 216, etc. As oneof ordinary skill in the art would appreciate, sound data storage module252 may automatically select which memory module 258 based on othercommands, data or circumstances. For example, if the user selects acertain data format or compression scheme, the resulting recorded sounddata 230 may be stored on one type of memory module 258. In anotherexample, should one type of memory module 258 not have sufficient memoryavailable to store sound data, then sound data storage module 258selects an alternative memory module 258 in which to store recordedsound data 230.

Referring to FIG. 2A, recorded sound data 230 may comprises one or moreof analog audio signal 220 generated by sound transducer 120, digitalaudio signal 222 generated by condition and ADC module 202, processedaudio signal 224 generated by DSP 204, and stimulation signal 226generated by converter module 206. In other words, sound data storagemodule 252 may record data from any stage along the sound processingpipeline, including sound data which has not been processed (that is,analog audio signal 220 and digital audio signal 222) and sound datawhich has been processed (that is, processed audio signal 224 andstimulation signal 226).

As noted, sound data-to-stimulus data converter 206 converts processedaudio signal 224 into a stimulation signal 226 suitable for delivery toelectrode array 134, and that such operations typically include theapplication of user-specific parameters to customize the electricalstimulation signals for the particular recipient. As a result, inembodiments described herein in which sound data 230 stored in memorymodule(s) 214 includes sound data 230D having a content as that ofstimulation signal 226, recipient-specific parameters are either notutilized or recipient-specific parameters are applied to stimulationsignal 226 prior to its storage in memory module(s) 214.

It should also be appreciated that sound data storage module 252 recordssound data that is representative of ‘live’ sounds; that is, soundsignals currently being received by sound transducer 120 and which isnot processed, partially processed or completely processed by soundprocessor 200. In other words, embodiments of sound data storage andretrieval system 228 are capable of effectively making live soundrecordings.

As shown in FIG. 2B, sound data storage module 252 receives for storagesound data 260 from programming system 142 via programming interface 214and sound data 262 from removable memory module 258A. As such, removablestorage media may also be used to store recorded entertainment such asMP3 music files, allowing the recipient to enjoy such program materialthus avoiding the inconvenience of additional devices andinterconnecting cables.

In addition to the source of sound data 230, sound data storage andretrieval system 252 may also be configured to record the selected sounddata in accordance with a specified recording period 270. Recordingperiod selection command 270 specifies the particular portion of theidentified source data 230A-230D which is to be recorded. For example,the selected sound data may be recorded between a begin record and endrecord indication, at certain specified time periods, continuously, fora specified duration, and the like.

Sound data storage and retrieval system 228 determines the content andduration of recorded sound data 230 based on a sound data contentselection command 268 and a recording period selection command 270.Commands 268 and 270 may be generated by any of the components ordevices which system shares an interface such as system controller 212,sound processor user interfaces 216, etc. As one of ordinary skill inthe art would appreciate, sound data storage module 252 mayautomatically select which stage 120, 202, 204, 206, 208 or 210 fromwhich sound data 230 is to be recorded based on other commands, data orcircumstances.

Sound data storage module 252 is further configured to store recordedsound data 230 in any format (including compression) desired orrequired. For example, sound data can be stored in any one of severaldifferent formats depending on the sound data content, storage settings272. Storage settings 272 may be provided by the recipient, via userinterfaces 214 or via programming device 142. In one embodiment, thechoice of data storage format is made continuously and automatically bysound processor 200 or other component of hearing prostheses 100, andprovided to sound data storage and retrieval system 228 via, forexample, system controller 212. In such an embodiment, the assigned datastorage format might therefore change in real-time to accommodatechanging conditions.

Such data formats may include, but are not limited to a continuous orintermittent serial bit stream representing the original sound signal,compressed MP3 format, indexed regular expression types of datacompression, sound feature extraction and compression in time andfrequency domain, or data representing the stimulation current whichmight be delivered to the recipient.

The format and compression may be selected, for example, so as tooptimize various operating parameters which include data storagecapacity, storage rate, retrieval speed and battery energy consumptionefficiency. For example, in one embodiment the format of recorded sounddata 230 is selected so as to allow one or more days of sound to becontinually recorded using low sample rates and MP3-type sound datacompression.

In addition to storing recorded sound data 230, sound data storagemodule 252 also stores associated data 274 prior to, simultaneouslywith, or subsequent to the storage of recorded sound data 230.

In some embodiments, associated data 274 comprises one or more labels,so that the recipient can select which recorded sounds 230 are to beretrieved and processed by sound processor 200. In one embodiment, forexample, associated data 274 comprises a timestamp that may be used totrigger the retrieval of sounds recorded at a selected time.

In another embodiment, associated data 274 includes a difficult statusor rating provided by the recipient. Such information can be utilized,for example, when the sound data storage and retrieval system 228 iscontinuously recording sound data 230. During such real-time recording,the recipient can identify which recorded sound data 230 includes soundsthe recipient had difficulty perceiving. Hence, the recipient, uponencountering a problem in perceiving a ‘live’ sound, may, for example,press a button on a user interface 214 which causes system 228 to labelthe current or last stored recording with an indication that a difficultsound is included. Such relabelling will assist in retrieving therecording for later retrieval and play back. Potentially, also, suchrelabelling could assist in a clinical analysis by a hearing specialist144.

In effect, this allows the recipient to ‘replay’ sounds previouslyprovided as stimuli. In this way, if a recipient missed sounds the firsttime, the recipient can command the system to replay the recorded sounddata, repetitively if desired. In the embodiment illustrated in FIG. 2B,such a selection is provided to sound data retrieval module 254 as aselection criteria command 280 provided, for example, via userinterfaces 216 or programming interface 214.

In the same or other embodiments, recorded sound data 230 is labelledwith a file name, a time stamp to indicate the date and time of day whenthe data was acquired and stored, and a summary of the data content ofthe file. Such summary can include, but is not limited to, the durationof a sound data recording, spoken words or phrases which might beattached by a recipient to facilitate latter retrieval, or key sounds orphrases identified by the recipient at the time they were heard andrecorded.

The recipient may also provide sound data retrieval module 254 with areplay characteristics command 282. For example, replayed sounds can bepresented to the recipient at a different apparent replay speed andpitch from the original sound 103 as specified in command 282. Slowingthe rate at which a recorded conversation is presented to the recipientwhile raising the pitch of low frequency voice formants can greatlyincrease the recipient's comprehension of speech. Similarly, theduration of any pauses in recorded speech may be increased or decreasedat the recipient's discretion. As one of ordinary skill in the art wouldappreciate other characteristics of the retrieved sound 232 may becontrolled in alternative embodiments of the present invention.

Once the desired recorded sound 230 is selected based on search criteria280, and the desired playback characteristics are set based on replaycharacteristics 282, the recipient may initiate retrieved sound data 286by generating replay command 284.

As shown in FIG. 2B, retrieved sound data 286 is provided to a dataextractor module 254 to reconstitute the retrieved sound data into aform suitable for delivery to the desired destination 290 such asprogramming interface 214 or a particular stage 202, 204, 206, 208, 210of the sound processor pipeline.

As noted, recorded sound data 230 may comprises one or more of analogaudio signal 220 generated by sound transducer 120, digital audio signal222 generated by condition and ADC module 202, processed audio signal224 generated by DSP 204, and stimulation signal 226 generated byconverter module 206. In other words, sound data storage module 252 mayrecord data from any stage along the sound processing pipeline,including sound data which has not been processed (that is, analog audiosignal 220 and digital audio signal 222) and sound data which has beenprocessed (that is, processed audio signal 224 and stimulation signal226).

As such, retrieved sound data 232 may or may not be processed by DSP204. For example, if recorded sound data 230 is stored in a formrepresentative of stimulation signals 226, the corresponding retrievedsound data 232 requires little or no processing and the retrievedstimulation signals may be provided directly to the implanted neuralstimulator 126. Similarly, should recorded sound data 230 be stored in aform representative of digital audio signals 222, the correspondingretrieved sound data 232 will be processed by the remaining portions ofthe sound processor pipeline, namely DSP 204, converter 206, encoder 208to form electrical stimulation signals as described above.

It should be appreciated that in certain embodiments or under certaincircumstances while stored sounds are being retrieved and processed bysound processor 200, real-time or “live” sounds received via soundtransducer 120 are not simultaneously processed through sound processor200 and provided as stimuli to the recipient. As such, when sound datastorage and retrieval system 228 is invoked to retrieve sound data 232,system controller 212 temporarily interrupts or reduces the perceivablelevel of live sound 103 in some embodiments of the present invention.

This ability to selectively recall sounds of interest is particularlybeneficial for recipients of hearing prostheses that use electricalstimulation either whole or in part, to evoke a hearing or hearing-likesensation. The successful habilitation of such recipients can be limitedby the spatially discontinuous manner in which a finite number ofstimulating electrodes 136 of the implanted neural stimulator 126 canstimulate the recipient and invoke a realistic sense of hearing. Thismay improve outcomes for such recipients by providing a differentapproach to improving the habilitation and/or ability to recognizenoises.

Sounds that have been stored and identified by the recipient asdifficult to understand can, for example, be recalled and uploaded to acomputer then emailed to the user's hearing professional 144. Subsequentanalysis would then empower the hearing professional to refineprosthesis settings to better serve the recipient's future understandingof such identified sounds.

As an illustrative example of a scenario where this is of benefit,picture a recipient in a noisy environment, for example a train station,and a message is announced on the public address system. Due to thelimitations imposed on sound processor 200 for approximate real-timeprocessing of live sounds, the important sounds, that is, theannouncement, may not be perceived clearly by the recipient. By‘replaying’ the stored data representative of when the announcementhappened and allowing the processor more time to conduct more complexprocessing, the announcement can be perceived more clearly with much ofthe background noise eliminated.

As another illustrative example; a recipient encounters an environmentalsound such as the ring of a doorbell. The recipient may be unable tointerpret this sound if sound processor 200 is configured to optimizehuman speech while excluding background noise. By activating the re-callcontrol, the sound of the doorbell can be played back to the recipient,only this time using speech processor settings intended to optimizeenvironmental sounds.

A further benefit of the ‘record’ and ‘replay’ functionality arises inspeech habilitation. Impaired speech frequently arises in persons withcompromised hearing, as they are unable to accurately hear and comparetheir own voice to that of others. With the present system, a recipientcan ‘record’ their own voice and selectively ‘replay’ the recording tohear what their voice sounds like. In this way, recipients can capture,identify and correct the parts of their own speech which others finddifficult to understand.

In another embodiment, a sound recognition comparator 215 detects whenan incoming or replayed sound, or the attributes of an incoming orreplayed sound, closely match those of a sound, or collection of soundattributes, stored previously. In the embodiment shown in FIG. 2A, soundrecognition comparator 215 is included in system controller 212,although that need not be the case.

The recognition of specific sounds or categories of specific sounds canbe used to trigger functional changes in the operation of theprosthesis, for example adjustment of control settings of soundprocessor 200 in response to commands spoken by the recipient or others.

Additionally or alternatively, the recognition of specific sounds orcategories of specific sounds can be used to deliver a different orsubstitute sound in response to that of a recognized sound. Spokenphrases substituted for incoming sound can alert the recipient about theapproach of a speeding motor vehicle, the sound of a door bell or thecry of a baby. In this way, translation from one spoken language toanother can be implemented.

Aside from recipient-initiated ‘play’ of stored sounds, there can bebenefits from having automatically triggered ‘play’ of stored sounds. Asan example, certain types of sounds may be of particular interest to therecipient, e.g. a telephone ringing, a baby crying or a fire alarm. Inwhich case, it is important to the recipient that such sounds areperceived, or when not perceived their occurrence is alerted to therecipient. In exemplary embodiments of the present invention, the soundrecognition comparator 215 recognizes such important sounds from theincoming electric audio signal. In the event of an important sound beingdetected, sound data storage and retrieval system 228 can be triggeredto retrieve respective data from memory module(s) 258. The respectivedata stored may be an isolated recording of the important sound.Alternatively, the data stored could be a voice recording made by therecipient describing the important sound, e.g. “my baby is crying”, “thefire alarm is sounding”, “the telephone is ringing”. In suchembodiments, user interface 216 may include some form of programmingfunction to allow a recipient to program the system to recognizeparticular sounds and label particular stored data to be triggered inresponse to such sounds being detected.

When the data is stored in the format of electric audio signals 252 or254, sounds which are to be ‘replayed’ are reprocessed by soundprocessor 200. Since the ‘replayed’ sounds are not required to beprocessed in approximate real time, more time may be given to thereprocessing which allows more complex or different processing to beapplied. In this manner, the ‘replayed’ sounds are provided as stimulito the recipient with improved clarity than when the sounds wereoriginally processed in real-time. Such additional processing isattained by system controller 212 controlling the pertinent stages 202,204, 206, 208, 210 of the sound processing pipeline. In one embodiment,repetitive processing is attained by data extractor 256 convertingretrieved sound data 232 to the content necessary for processing by thedesired stages, including DSP stage 204, of the sound processingpipeline.

In some embodiments, the playing of sounds can include thereconstruction of voice sound signals from data stored as ASCII text. Incertain embodiments, sound data extractor module 256 also comprises aspeech synthesizer such as that described in International PublicationNos. WO0097/001314, which is hereby incorporated by reference herein, toconvert such data to sound signals which may then be converted further,if necessary, for processing by the desired stages of the soundprocessing pipeline.

FIG. 3A is a flow chart of certain aspects of a process 300 in whichoperations of one embodiment of the present invention are performed.

At block 302, sound transducer 120 converts incoming sound into ananalog electrical audio signal 220.

At block 304, analog signal 220 is conditioned in amplitude and spectralresponse, and then the conditioned analog signal is converted into adigital signal for further processing. The analog signal conditioning isconducted in accordance with customized parameters derived from a systemcontrol memory 402. Such customized parameters are optimizedrecipient-specific parameters which are typically established andprogrammed into system control memory 402 in consultation with a hearingclinician. The resulting audio signal is digitized at block 306.

At block 308, the converted digital signal 222 is processed by DSP 204to enhance sounds of interest and to minimize unwanted sounds and noise.The customized parameter control is derived from system control memory350.

At block 310, potentially more sophisticated digital signal processingis conducted on digital audio data 222 to further enhance the signal forthe purposes of recipient perception. As noted, for “real time” signalsthere are limitations on the potential for conducting more sophisticatedprocessing. Hence, at this stage in the process, it is convenient toprovide the interaction with sound data storage and retrieval system200, the operations of which are illustrated in FIG. 3B.

Preferably, all ‘real time’ data is continuously packaged 352, that is,labelled and formatted for storage, and then stored 354 into memory 258.Ideally, continuously stored data is stored in blocks of discrete time,for example, 60 seconds, of incoming sound 103.

At block 310, data retrieved from memory 258 may be subjected to thesophisticated digital processing. Data retrieval may be initiated byrecipient selection, in which case the selected sound data is searchedfor and retrieved from memory. In exemplary embodiments, the dataretrieval may be initiated automatically, for example where the ‘realtime’ sound signal includes a predetermined sound signal which, upondetection, triggers the retrieval of corresponding stored data to be‘played’ to the recipient in place of the live sound. In such cases, theprocessing at block 310 includes signal analysis to detect the presenceof predetermined sounds, which may be derived from the system controlmemory 350 for the purpose of comparison.

Ideally, at block 310, where retrieved data is to be processed andprovided to the recipient as perceivable stimuli, ‘real time’ signalsare suppressed to prevent the recipient experiencing confusing output.However, while the ‘real time’ signals are suppressed, they are stillpackaged and stored for subsequent retrieval, if desired or required.

At block 312, the ‘real time’ digital signal or retrieved digital signalis further processed to extract and quantify dominant spectralcomponents. Following this, at 314, selected spectral components arefactored with customized recipient neural stimulation parameters,derived from system control memory 350, producing a stimulation signal.

In cases where sound processor 200 is separate from the implantedstimulator 126, the processed digital data is encoded at block 316 andconverted for the purposes of wireless transmission 358 to implantstimulator 126 and its internal processes.

FIG. 3C is a flow chart of one embodiment of the operations performed inimplanted assembly 144 of cochlear implant 100. At 380, the wirelesstransmission is received and converted into a digital signalrepresentative of the stimulation signal. At 382, the digital signal isconverted into discrete channels of stimulation signals which is thenprovided to the implant's electrode system to provide, at block 384,stimulating currents to the targeted neural stimulation sites of therecipient thereby providing perceivable sound to the user.

While the present invention has been described with reference tospecific embodiments, it will be appreciated that various modificationsand changes could be made without departing from the scope of theinvention. For example, it is anticipated that the main functionalelements of the present invention could be applied as an upgrade modulefor existing prosthesis systems. In this regard, it is expected that theprocessing, controller and memory components could be provided in theform of an upgrade module for replacing the processing and controlcapabilities of existing prosthesis systems. As another example, itshould be appreciated that the allocation of the above operations areexemplary only and that the functions and operations of the presentinvention may be implemented in other or one single component,subsystem, or system. As just one example, sound data storage andretrieval system 228 may be implemented completely in system controller212 in alternative embodiments of the present invention. As anotherexample, sound data storage and retrieval system 228 other than memorymodules 258 may be implemented in system controller 212 in alternativeembodiments of the present invention. As another example, in alternativeembodiments, sound processor 200 is incorporated into an auditory brainstem hearing prosthesis, or other neural stimulation implant device. Insuch embodiments, sound processor 200 is hard-wired with the prosthesisand the stimulation signals are provided directly to the device forapplication as stimuli to the neural hearing system of the recipient.Alternatively, the sound processor is physically separate from theimplant device. In this case, the stimulation signals are provided byway of wireless signals from a transmitter, associated with theprocessor, to a receiver incorporated with the implant device. As afurther example, in embodiments in which sound processor 200 isimplemented in a hybrid hearing prosthesis that delivers electrical andmechanical (acoustical or electro-mechanical) stimulation to arecipient, retrieved sound data 232 may be recorded by one subsystem,for example, the cochlear prosthesis, and played back in anothersubsystem for possible improved perception. In a further example, inalternative embodiments, sound data storage and retrieval system 200 maybe implemented by a file handling system. In another example, the aboveaspects of the present application are supplemented with features ofInternational Publication No. WO97/01314 filed on Jun. 28, 1996 which ishereby incorporated by reference herein in its entirety. Accordingly, itwill be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive.

Another aspect of the present invention is described next below withreference to FIGS. 4 through 17. In a broad form, this aspect of thepresent invention provides a speech-based interface between a soundprocessor and the recipient. The system generates speech, from recordedor other sources, which is supplied using the prosthesis to therecipient. Thus, the recipient will hear a message in understandablespeech, for example ‘battery low’, rather than a series of tones.

This aspect of the present invention is principally described withreference to implementations for cochlear implants of conventional type.However, it will be understood that the present invention is broadlyapplicable to other types of hearing prostheses, such as brain stemimplants, hearing aids and the like.

Generally, a sound processor would be able to ‘speak’ to the recipientto provide them with information as required by the system design.Information or warnings from the sound processor are issued to therecipient using recorded or generated speech segments. For example, thesound processor plays back a recorded speech sample, such as ‘program 2’or ‘battery low’ when required.

This could also extend to a range of built in self check systems,diagnostics, implant test, remote control test, complicated feature ormenu systems (“choose from the following options . . . ”), etc. Once thefacility is provided, it will be apparent that it can be used in avariety of circumstances.

Prior art FIG. 4 shows the basic signal processing path for a typicalcochlear implant speech processor. Sound originates at microphone 410,is the digitized by one or more analog-to-digital converters (ADC) 420,possibly through an Automatic Gain Control (AGC) and sensitivityadjustment 430, through to a filter bank 440. The signal is thenprocessed with a cochlear implant speech coding strategy, such as ACE,in the sampling and selection stage 450. The signals are then mapped 460into the electrode map for the recipient, encoded by the data encoderformatter (DEF) 470, for transmission via the RF coil 480 to theimplant. This is described so as to explain the basic, existing systemwithout the addition of the present invention, so that the variousimplementations described below will be better understood. The operationof such an implant system as shown in FIG. 4 is well understood in theart, and is implemented in commercially available systems.

One implementation of this aspect of the present invention is shown inFIG. 5. Take for example a simple alarm condition with the speechprocessor, such as battery low. When the speech processor software orhardware detects this condition, signal path controller 590 becomesoperative. It is noted that existing processors are arranged todetermine and indicate this condition, and that the present embodimentis concerned with how this is communicated to the recipient.

According to the embodiment of FIG. 5, once the alarm condition isestablished, the microphone 510 is switched out of the input, so that astored digital audio signal in memory 595 can be delivered to the speechprocessing system. The signal path controller 590 may also disable anyadaptive functions in the signal path, such as compression, that wouldaffect the playback of the sound. The signal path controller 590 wouldthen select the required audio signal, and start the output of thememory into the signal path, replacing the usual input from the analogto digital converter 520.

It is also possible to mix the playback of the sound message with theincoming microphone audio. In either case, the recipient would hear thespeech segment ‘battery low’ at a predefined volume level, which willprovide a much more readily understood message than a set of beeps.

The ability to mix the playback of the sound message with the incomingmicrophone audio would provide minimal interruption to the environmentbeing listened to by the recipient, since the signal from the microphone510 is still heard. The amplitude ratio for which the two signals arecombined could be programmable. A typical mixing ratio might be 3:1;that is, the microphone signal is set to a third of the amplitude of thesound message signal. The signal path controller 590 may also choose tomix the sound message in with the microphone signal at a point after thefront end processing is complete, so that the sound message is notmodified by these functions. This is shown in FIG. 9.

In order to ensure each sound message is always heard at a predefinedvolume level, a method could be applied whereby for example the RMSlevel of each sound message is adjusted before downloading to the speechprocessor to a set target level. During playback this target level isthen mapped to a particular volume that is comfortable for therecipient. This level could be adjusted for each recipient as required.

One example of a complete operation of the sound message function beingused for a ‘battery low’ alarm is given below in pseudo code:

If (Notification = True) % There is an alarm condition % Setup thesignal path for the sound message: Call SignalPathController(AGC=Off,ASC=Off); Call SignalPathController(MicrophoneSignal=Off); Alarm =IdentifyAlarm( ); % Find out which alarm Select Case (Alarm) % Decidewhich message Case BattEmpty: CallPlayMessage(BATT_EMPTY_MESSAGE): CaseBattLow: CallPlayMessage(BATT_LOW_MESSAGE); End Case; % Return thesignal path to how it was before Call SignalPathController(AGC=On,ASC=On); Call SignalPathController(MicrophoneSignal = On); Return;

The BATT_EMPTY_MESSAGE and BATT_LOW_MESSAGE values could be, forexample, pointers to the required sampled speech data to be played.

The data storage format of the sampled speech messages at its simplestimplementation would be such that when played through the signal path,the sound is presented to the recipient as though received through themicrophone 510. For example, if the ADC 520 in the system is a 16 bit16000 Hz device, then the speech segments comprising each message shouldalso be pre-recorded in this format, preferably with a similar type ofmicrophone. However, this form of data may lead to storage issues withlarge digital files. One way to avoid this is to use speech compressionto reduce the memory requirements needed, such as Linear PredictiveCoding (LPC). Any type of conventional speech compression could be used.This would lead to a reduced memory requirement. FIG. 6 shows animplementation of this type, where an additional decompression stage 697is required.

By way of example, a message that might be required to be implemented inthe system is the segment of speech “You have 10 minutes battery liferemaining”. An example waveform 1020 of this segment is shown in FIG.10, which was recorded with a standard PC sound card at 16000 Hzsampling rate, 16 bit resolution, and with one channel of audio (mono).The segment lasts approximately 2.25 seconds, required 35,463 samplesand has a raw storage requirement of approximately 70 kB (kilobytes).

In FIG. 11 is shown a signal flow diagram of the analysis part of atypical Linear Predictive Coder (LPC) 697. This coder is based onLevension-Durbin recursion, and is well described in the literature. Theanalysis part of this type of LPC is used to derive a compressedrepresentation of a speech signal, by expressing the signal in terms ofa set of filter coefficients and an excitation signal to match thesecoefficients. The excitation signal is also known as a residual.

The analysis part of this type of LPC would typically be implemented inthe fitting software for the hearing instrument system, or used duringdevelopment to pre-calculate the compressed representation for eachspeech message and language required. The pre-calculated representationcould then be provided as stored data in either the fitting software fordownloading into the hearing instrument at fitting time, or if spacepermits, entirely within the hearing instrument during manufacture.

The coefficients and excitation signal are derived for small segments ofthe speech signal being analysed, typically 20 milliseconds in lengthand overlapping by 10 milliseconds, such that together the entire speechmessage is represented by concatenated analysis segments. A signal flowdiagram shown in FIG. 11 gives an example implementation of this method.The output from the analysis stage therefore consists of multiple setsof filter coefficients corresponding to each segment of the speechhaving been analyzed, and corresponding excitation signal of length innumber of samples similar to the original signal. FIGS. 12 and 14 showexamples of the calculated multiple coefficient sets 1200 andcorresponding excitation signal 1500 respectively for the segment ofspeech “You have 10 minutes battery life remaining”.

The coefficients and excitation signal are typically then quantized forefficient storage by 5 bits 1300 and 6 bits 1500 respectively, as shownin FIGS. 13 and 15. For the segment of speech “You have 10 minutesbattery life remaining”, the storage requirement is approximately 30 kB(kilobytes), a saving of close to 2.5 times the raw data requirement forthe same speech segment.

In FIG. 16 is shown a signal flow diagram of the synthesis part of theexample Linear Predictive Coder (LPC). The synthesis part is responsiblefor reconstructing an approximation of the original speech signal usingthe coefficient sets and excitation signal provided by the analysis partof the LPC. The synthesis part is required to be implemented in thehearing instrument in order to decompress the speech messages on thefly, as required. LPC Synthesis operates by applying each coefficientset in turn to an all pole IIR filter 1610 for each equivalent synthesiswindow, and applying the excitation signal as input to the IIR filter.The output 1620 of the IIR filter 1610 is the decompressed speechmessage for use as input to the signal path of the speech processor asrequired. FIG. 14 shows and example of the IIR filter 1610 output forthe segment of speech “You have 10 minutes battery life remaining”. Thesimilarity to FIG. 10 will be recognized.

A further alternative implementation is to sample and store the speechmessages as 8 kHz, 16 bit sampled data, and then interpolate up to therequired playback sample rate of 16 kHz for example on playback.

A further alternative implementation is to store the speech messages asstimulation data, which has already been pre-processed through therecipient's map settings, or a portion of them. The pre-processing inorder to provide the data in this format could be accomplished eitherduring the detailed design of the product for all possible map settings,or at fitting time with the appropriate function implemented in theclinical software. In either case, only the required data is downloadedinto the speech processor during fitting. This has the advantage thatthe behaviour of the signal path may be no longer important (or at leastless so), as for example the data may be played directly out the speechprocessor, via the Data Encoder Formatter (DEF). The data size of thespeech segments may also be more optimal at this point. FIG. 4illustrates an implementation using the point of the signal path beforethe DEF 470, 570, 670, 770, 870. 970. In this case, the required messagedata simply replaces the normal signal stream for the period of timerequired. Similarly, the speech signal could be provided by using asignal appropriate for another part of the signal path, and insertingthat signal. These approaches need to be carefully integrated with thesignal processing system, so as to not interfere with, for example, anyfeedback controlled level or signal priority mechanisms which may affectsubsequent processing.

One example of how safe operation might be achieved is given below in afurther elaboration of the pseudo code presented above. When a speechmessage notification is required, the state of the speech processorshould be checked and modified to be suitable first.

If (Notifiction = True) % There is an alarm condition % Setup the signalpath for the sound message: Call SignalPathController(AGC=Off, ASC=Off);Call SignalPathController(MicrophoneSignal = Off); % Check what adaptiveprocesses are running: If (ChannelGainsStable = False) CallStopChannelGain Adaptation; % Pause adaptation ChannelGainsStopped =True; end if; If (VoiceActivityDetector = True) CallStopVoiceActivityDetector; % Pause detector VoiceActivityDetectorStopped= True; end if; Alarm = IdentifyAlarm( ); % Find out which alarm SelectCase (Alarm) % Decide which message Case BattEmpty:CallPlayMessage(BATT_EMPTY_MESSAGE); Case BattLow:CallPlayMessage(BATT_LOW_MESSAGE) End Case; % Return the adaptiveprocesses to how they were before If (ChannelGainsStopped = True) CallReStartChannelGainAdaptation;%Restart adaptation end if; If(VoiceActivityDetectorStopped = True) Call ReStartVoiceActivityDetector;% Restart detector end if; % Return the signal path to how it was beforeCall SignalPathController(AGC=On, ASC=On); CallSignalPathController(MicrophoneSignal = On); Return;

A further example would be to store the speech samples as stimulationdata in NIC format, as described in the present applicant's co-pendingPCT application, published as WO 02/054991, which is hereby incorporatedby reference herein in its entirety. This has the advantage that the NICformat is also compact (since it incorporates loops for example) and theNIC tools are convenient and very flexible to use. Implementation usingthis format would require an NIC interpreter 895 in order to decode theNIC format data 897, as shown in FIG. 8.

It will be appreciated that the present invention is not limited to anyspecific mechanism for providing speech input to the prosthesis. Forexample, although not presently preferred, the speech signal could begenerated in principle via a speech synthesizer, rather than storedfiles. Functionally, what is required is that the speech message isgenerated in response to an indication by the sound processor orprosthesis that a system level communication is required, and that thisis provided using an input to the existing signal pathway for providingstimulus signals to the recipient.

The language spoken by the sound processor can be chosen at fitting timein the clinic, where the clinician would use programming software tochoose which set of speech samples to download into the device.

The playback of speech messages is not limited to warnings of events. Itcan be used to construct an elaborate menu system which would otherwisebe impossible to implement without many more buttons or displays. Forexample, the processor could prompt ‘push the program button to testyour microphones’.

Any discussion of documents, acts, materials, devices, articles or thelike which has been included in the present specification is solely forthe purpose of providing a context for the present invention. It is notto be taken as an admission that any of these matters form part of theprior art or were common general knowledge in the field relevant to thepresent invention as it existed before the priority date of each claimof this application.

What is claimed is:
 1. A hearing prosthesis for delivering stimuli to ahearing-impaired recipient, comprising: a sound transducer forconverting received sound signals into electric audio signals; a soundprocessor for converting said electric audio signals into stimulisignals; a stimulator for delivering said stimuli signals to therecipient; a memory for storing data representative of said receivedsound signals; and a controller configured to cause selected sound datato be retrieved from said memory and processed by said sound processor.2. The hearing prosthesis of claim 1, wherein said stored data is in theform of electric audio signals which said processor, upon retrieval,converts into stimuli signals.
 3. The hearing prosthesis of claim 1,wherein said stored data is in the form of partially or fully processedstimuli signals.
 4. The hearing prosthesis of claim 1, further includinga user interface for allowing a user to select data stored in saidmemory and trigger said controller to cause said selected data to beretrieved.
 5. The hearing prosthesis of claim 1, wherein said system isarranged to detect the presence of a signal with predeterminedcharacteristics, corresponding to data stored in said memory; wherein,upon detecting the presence of a predetermined signal, said controlleris triggered to cause said corresponding data to be retrieved.
 6. Thehearing prosthesis of claim 5, wherein said corresponding datarepresents a voice message describing the predetermined signal or asystematic pattern of stimuli that is recognizable to the user.
 7. Thehearing prosthesis of claim 1, wherein said controller is adapted tocause data, representative of an electric audio signal output from saidsound transducer, to be stored in said memory.
 8. The hearing prosthesisof claim 7, wherein said user interface allows said user to actuate saidcontroller into causing said data to be stored.
 9. The hearingprosthesis of claim 1, wherein said controller, upon being triggered,partially or fully inhibits the delivery of other data to the stimulatorwhile said selected data is being retrieved and conveyed to the user.10. The hearing prosthesis of claim 1, wherein, when said selected datais previously delivered sounds signals, said signals are processed in analternative manner to those originally conveyed to the user.
 11. Thehearing prosthesis according to claim 1, wherein said stimulator isincorporated in a cochlear implant.
 12. The hearing prosthesis accordingto claim 1, wherein said stimulator receives stimuli signals wirelesslyfrom said processor.
 13. A method for delivering stimuli to ahearing-impaired recipient, comprising: converting received soundsignals into electric audio signals; converting said electric audiosignals into stimuli signals; delivering said stimuli signals to therecipient; storing data representative of said received sound signals;retrieving selected sound data from said memory; and processing saidretrieval sound data by said sound processor.
 14. The method of claim13, further comprising: receiving a user input selecting said sound datastored in said memory.